The present invention relates to a thermostatic coolant circulating device that circularly supplies a thermostatic coolant to a load.
FIG. 2 shows one example of a known thermostatic coolant circulating device. This thermostatic coolant circulating device has a coolant circuit 2 for circularly supplying a thermostatic coolant to a load 1, a refrigerating circuit 3 for cooling the aforesaid coolant having its temperature raised by cooling the load 1, and a control section 4 that controls these circuits 2, 3.
In the aforesaid coolant circuit 2, the coolant having its temperature raised by cooling the load 1 refluxes through a return pipe 6 into a heat exchanger 7. After the coolant is cooled below a set temperature in this heat exchanger 7 by heat exchange with a refrigerant flowing through an evaporator 8 of the aforesaid refrigerating circuit 3, the coolant flows into a heating vessel 9 to be heated up to a set temperature by a heater 10, and then overflows this heating vessel 9 to flow into a tank 11. Then, the coolant is supplied through a supplying pipe 13 to the aforesaid load 1 by a pump 12. The temperature of the aforesaid coolant is measured by a temperature sensor 14 disposed at an outlet of the tank 11, and the aforesaid heater 10 is controlled by the control section 4 so that the temperature measured here will be the set temperature.
On the other hand, in the aforesaid refrigerating circuit 3, the refrigerant evaporated by heat exchange with the coolant in the aforesaid evaporator 8 is compressed by a compressor 15 into a high-temperature high-pressure refrigerant gas. This refrigerant gas is cooled by a condenser 16 to be condensed into a high-pressure liquid refrigerant. Then, the temperature of this liquid refrigerant is lowered by reducing the pressure thereof by means of a constant-pressure expansion valve 17 for supplying it to the aforesaid evaporator 8. The flow rate of the refrigerant circulating through the circuit is always maintained constant by the aforesaid constant-pressure expansion valve 17. Therefore, the cooling capability of this refrigerating circuit 3 is always constant irrespective of whether the thermal load is larger or small.
Thus, in the conventional coolant circulating device, the coolant having a raised temperature is cooled below the set temperature by the refrigerating circuit and then heated up to the set temperature by the heater, necessitating the use of the heater at all times and leading to large electric-power consumption. Particularly, in the case where the temperature of the coolant does not rise so much due to a small heat quantity of the load, the aforesaid coolant is cooled more than necessary to an excessively low temperature. In order to heat it up to the set temperature by the heater, an extremely large heat quantity has been required. Moreover, in the case where the temperature of the aforesaid coolant is higher than an external atmospheric temperature, a temperature decrease caused by heat dissipation to the outside is added to further lower the temperature of the coolant, thereby requiring a further large heat quantity to heat it to the set temperature. As a result of this, the capability of the heater will necessarily be larger; related equipment will be larger; and the maximum operation current and the electric power consumption will be larger, leading to increase in the running cost, the equipment cost, and others.
A principal technical object of the present invention is to provide a thermostatic coolant circulating device having a good operation efficiency and being economical in which a coolant having a temperature raised by cooling a load can be maintained at a set temperature in a refrigerating circuit by allowing the cooling capability of the aforesaid refrigerating circuit to be adjustable in accordance with a temperature rise of the coolant.
Another technical object of the present invention is to use a heater auxiliarily in the aforesaid coolant circulating device for raising the temperature of the aforesaid coolant in the case where the temperature rise of the coolant by the load is small or in the case where the temperature of the coolant falls below the set temperature due to heat dissipation to the outside, thereby to achieve scale reduction of the aforesaid heater and reduction in the equipment cost for heating and the running cost.
In order to solve the aforesaid objects, the present invention provides a thermostatic coolant circulating device comprising a coolant circuit for circularly supplying a coolant to a load, a refrigerating circuit in which the aforesaid coolant having a temperature raised by cooling the load is cooled in a heat exchanger by allowing heat exchange with a refrigerant, and a control section that controls these circuits.
The aforesaid refrigerating circuit has a valve means capable of adjusting a flow rate of the refrigerant supplied to the aforesaid heat exchanger; the aforesaid coolant circuit has a temperature sensor for measuring the temperature of the coolant cooled in the aforesaid heat exchanger; and the aforesaid control section has a circuit means for adjusting an opening degree of the aforesaid valve means so that the temperature of the coolant measured by the aforesaid temperature sensor will be a set temperature.
In the coolant circulating device of the present invention having the aforesaid construction, the coolant having a temperature raised by cooling a load having a large heat quantity is cooled to a set temperature by the heat exchanger and is supplied to the load again. At this time, if the temperature of the coolant measured by the aforesaid temperature sensor is higher than the set temperature, the opening degree of the aforesaid valve means increases to increase the flow rate of the refrigerant flowing into the heat exchanger, whereby the cooling capability increases to lower the temperature of the coolant to the set temperature. On the other hand, if the measured temperature of the coolant is lower than the set temperature, the opening degree of the aforesaid valve means decreases to decrease the flow rate of the aforesaid refrigerant, whereby the cooling capability decreases to dissolve excessive cooling of the coolant and the temperature thereof is maintained at the set temperature.
Thus, the temperature of the aforesaid coolant is maintained at the set temperature by adjusting the cooling capability of the refrigerating circuit in accordance with the temperature of the coolant.
According to one specific embodiment of the present invention, the aforesaid coolant circuit has a tank for housing the coolant sent out from the aforesaid heat exchanger, a heater for heating and raising the temperature of the aforesaid coolant, and a pump for supplying the coolant in the aforesaid tank to the load; the aforesaid temperature sensor is disposed at an outlet of the aforesaid heat exchanger so as to be capable of measuring the temperature of the coolant before being heated by the heater; and the aforesaid control section has a function of energizing the aforesaid heater when the temperature of the coolant measured by the aforesaid temperature sensor falls below the set temperature by more than a predetermined value.
This makes it possible to maintain the aforesaid coolant at the set temperature by using the heater auxiliarily even if the temperature of the coolant rises only a little due to small heat quantity of the load or if the liquid temperature falls below the set temperature by heat dissipation to the outside atmosphere.
In other words, in the case where the temperature rise of the coolant by the load is small as described above or in the case where a temperature decrease occurs in an external pipe before and after the load by heat dissipation due to the temperature of the coolant being higher than the external atmospheric temperature, the temperature of the coolant is cooled below the set temperature by the heat exchanger even if the cooling capability of the aforesaid refrigerating circuit is restricted to the minimum. For this reason, the control section energizes the heater on the basis of a measurement signal from the aforesaid temperature sensor to heat the coolant to the set temperature.
Thus, the use of the heater is limited only to the case where the temperature rise of the coolant by the load is small or the case where the temperature of the coolant falls below the set temperature by heat dissipation to the outside, and it is an auxiliary use that compensates for the decrease. This allows use of a smaller heater as compared with a conventional device that makes use of the heater at all times, whereby the equipment cost is reduced and also the maximum electric current of use and the consumed electric power are reduced to lower the running cost.
According to a specific preferable embodiment of the present invention, the aforesaid refrigerating circuit has an evaporator disposed in the aforesaid heat exchanger, a compressor that compresses the refrigerant subjected to the heat exchange with the cooling water in this evaporator into a high-temperature high-pressure refrigerant gas, a condenser that condenses the refrigerant gas from this compressor into a high-pressure liquid refrigerant, and an expansion valve that lowers a temperature of the liquid refrigerant from this condenser by reducing a pressure thereof; and the aforesaid expansion valve is an electronic expansion valve capable of controlling an opening degree by an electric signal from the aforesaid circuit means and serves as the aforesaid valve means for adjusting the flow rate of the refrigerant.
Furthermore, in the present invention, the aforesaid control section is preferably capable of changing the set temperature of the coolant.